Material with permanent magnetic properties



Sept. 4, 1962 M. BAERMANN 3,051,933

MATERIAL WITH PERMANENT MAGNETIC PROPERTIES Filed Oct. 31, 1957 2Sheets-Sheet 1 S. .V- 2 6 o 0" 0 9 l0 0 1 o o o o o 0 l8 FIG-2 w 5"" "S"I; N 5 5 1. u N N ."SN s S I SN l3 n SN 5' "5 s N N l4 INVENTOR.

'MAX BAERMANN ATTORNEY Sept. 4, 1962 M. BAERMANN 3,051,983

MATERIAL WITH PERMANENT MAGNETIC PROPERTIES Filed Oct. 51, 1957 2Sheets-Sheet 2 INVENTOR. MAX BAER MANN ATTORNEY United States Patent3,051,988 MATERIAL WITH PERMANENT MAGNETIC PROPERTIES Max Baermann,Bensberg Wulfshof, Bezirk Koln (Rhine), Germany Filed Oct. 31, 1957,Ser. No. 693,604 Claims priority, application Germany Feb. 9, 1957 17Claims. (Cl. 18---12) This invention pertains to the art of permanentmagnets and more particularly to a material and method of manufacturingsame having permanent magnetic properties.

The invention is particularly applicable to material for, and themanufacture of, soft elastic articles of manufacture which must adhereto similar articles or to magnetically permeable supports and will bedescribed with particular reference thereto, although it will beappreciated that the invention is equally applicable to the manufactureof rigid articles of manufacture or where the magnetic field of thearticles produced is used for purposes other than being attracted toother magnetic supports.

In accordance with the present invention, a thermoplastic material hasincorporated therein as a filler material at some stage in theprocessing thereof to a final article of manufacture, permanent magneticmaterials in either powdered or granular form in quantities of 2080% byvolume.

By thermoplastic is meant a material which will pass through a liquid orlow viscosity phase during the heating thereof in the forming ofarticles of manufacture therefrom. As such, the permanent magneticmaterials will in essence essentially float in the liquid plastic andwhen subjected to an external magnetizing force, may orient themselvesin accordance with the present invention. Thus if the thermoplasticmaterial with the permanent magnetic powder is injected into a mold as aliquid while subjecting the material to a magnetizing field, thepermanent magnetic particles will become magnetized and tend toaccumulate corresponding to the polarization of the magnetizing fields.When the thermoplastic material hardens or thickens, the permanentmagnetic powders will be held in this position. When the permanentmagnetic materials are anisotropic there is a further advantage that theparticles will align themselves in their preferred position and will beheld in such position resulting in a further increase of the ultimatemagnetic field intensity.

Permanent magnetic materials usable with the invention are those, eitherisotropic or anisotropic, which can be mechanically crushed to asufiiciently small size or a combination of non-magnetic materials whichwhen mixed in powdered or granular form result in either isotropic oranisotropic permanent magnetic materials and which would then besubjected to magnetizing forces during the process of forming thethermoplastic materials.

Particularly suited for the present invention are the permanent magneticmaterials which are manufactured and sold in the powdered form. As manyof these materials oxidize readily, the further processing must be doneby excluding oxygen, for example, by wetting the materials withappropriate liquids or using protective gases. Softeners may also beemployed for this purpose.

Preferably the magnetic materials should offer a minimum ofpermeability. Typical of such materials are manganese-bismuth, so-calledoxide magnets of the iron-barium, iron-strontium type.

Further in accordance with the present invention, a method ofmanufacturing permanent magnetic articles is provided comprising thesteps of mixing a thermoplastic material as above defined with apowdered or granular non-magnetized permanent magnetic material, heatingthe mixture to a temperature such that the thermoplastic mate- 3,051,988Patented Sept. 4, 1962 rial has a low viscosity, forming the mixture tothe desired shape and simultaneously subjecting it to a magnetizingforce, and allowing the magnetized formed mixture to. cool.

The method of forming may be those customary in the technique of plasticmaterial in the production of plates, sheets, shaped rods or formedparts such as kneading, extrusion, rolling, molding, injection moldingor blowing, the magnetizing in any desired polarization either on thesurface or through the cross section taking place as the thermoplasticmaterial changes from the liquid or low viscosity state to the congealedor hardened state.

Whenever the mixture is to be extruded or injection molded, it is oftenadvantageous, in accordance with the invention, to form granules of themixture which facilitates the manufacture of the material and enables avery homogeneous product to be obtained.

Plastics particularly usable with the present invention are thesuperpolyamids which have a melting temperature of about 220 C.

Further in accordance with the present invention, apparatus is providedfor manufacturing articles from such material comprising means forforming the material through the desired shape at least in part of anon-magnetic material in combination with means having a fixedrelationship relative to the material while being formed for exerting amagnetizing field on such material.

For an extrusion machine, in accordance with the invention, there isprovided a forming nozzle of non-magnetic material preferably having athin wall thickness at one surface in combination with magnetizing meansmovable longitudinally of the nozzle synchronously with the speed ofmovement of the plastic material through the nozzle. Where the nozzle isrelatively straight, the magnetizing means can be in the form 'of anendless chain carrying the magnetizing poles longitudinally of thenozzle. Alternatively, the extrusion nozzle can extend in an arcuatemanner and the magnetizing poles can be mounted on a rotating disc orwheel rotating at a speed such that the poles synchronously move withthe speed of movement of the plastic material through the nozzle.

Where the plastic material is to be formed into fiat sheets by means ofcalender rolls, in accordance with the invention, one or both of thecalender rolls are formed of non-magnetic material and containing aplurality of circumferentially spaced axially extending magnetizingpoles, either rotating with the roller or supported on a separate shaft,but in either event, moving synchronously with the speed of delivery ofthe material from the roller.

Further, where the material is to be injection molded, in accordancewith the invention, at least one of the sections of the injection moldis formed of non-magnetic material having magnetizing poles inserted inrecesses thereof, the base of which recess is relatively thin.

The principal object of the present invention is the provision of a newand improved permanent magnetic material which is easily manufactured toany desired shape which has a maximum field strength for a given Weightof permanent magnetic ingredients and is simple and inexpensive.

Another object of the invention is the provision of a new and improvedmethod of manufacturing permanent magnetic materials wherein thepermanent magnetic materials may be concentrated in desired spotsthroughout the article.

Still another object of the invent-ion is the provision of a new andimproved method of manufacturing articles of manufacture made fromthermoplastic materials containing powdered permanent magnetic materialswherein the permanent magnetic materials are bunched or grouped toprovide maximum localized field strengths.

Still another object of the invention is the provision of a new andimproved apparatus for molding or forming articles from a mixture ofthermoplastic and perma nent magnetic material comprising means formoving the mixture through a forming operation and other means forsynchronously moving magnetizing fields with the mixture.

The invention may take physical form in certain parts and arrangementsof parts and certain steps and combinations of steps preferredembodiments of which will be described in detail in this specificationand illustrated in the accompanying drawings which are a part hereof andwherein,

FIGURE 1 is a side cross-sectional somewhat diagrammatrical view of anextrusion press and nozzle having the magnetizing poles mounted on anendless chain all illustrating an embodiment of the invention.

FIGURE 2 is a view somewhat similar to FIGURE 1, but showing themagnetizing poles mounted on the periphery of a wheel.

FIGURE 3 is an end elevational view of calendering rolls with one of therolls having magnetizing poles mounted thereon illustrating analternative embodiment of the invention, and

FIGURE 4 is a side cross-sectional view of an injection mold showingsomewhat diagrammatically built-in magnetizing magnets.

Referring now to the drawings wherein the showings are for the purposesof illustrating preferred embodiments of the invention only and not forthe purposes of limiting same, FIGURE 1 shows a plastic material 1 beingextruded under the effect of a worm 2 through an extrusion nozzle 5heated as is conventional .by heating coils 3 and 4. The material 1, inaccordance with the invention, is formed of a mixture of:

(a) Any of the known thermoplastic materials capable upon heating toelevated temperatures of liquifying or having a low viscosity preferablya superpolyam-id, and,

(b) Any of the known permanent magnetic materials capable of beingcrushed or ground to granular or powdered form and preferably having aminimum permeability suoh as the manganese bismuth compounds or thevarious known oxide magnets, e.g., Without limitation, iron-barium oriron-strontium.

The permanent magnetic materials preferably have a volume of 6070% ofthe total of the material 1 although the volume may range from 20-80%.

The heating coils 3, 4 heat the material 1 above the plastic orliquifying temperature of the thermoplastic portions thereof.

This material 1 in a plastic state is advanced longitudinally throughthe nozzle 5 which has a relatively thin wall 6 of non-magneticmaterial. A plurality of permanent magnets are arranged in closerelationship to this wall 6 for the purpose of imposing a plurality oflongitudinally spaced magnetizing fields on the material 1 in the nozzle5. These magnets 10 are mounted on an endless chain 9 in turn supportedon a pair of sprocket wheels 7, 8. The sprocket wheels '7, 8 are rotatedby external power means not shown at a speed such as to move the magnets10 longitudinally of the nozzle 5 at a speed synchronous with the speedof movement of the material 1 through the nozzle 5. As the arrangementsfor maintaining this synchronous speed are well known to those skilledin the art, this apparatus is not more specifically shown.

The far end of the nozzle 5 is cooled by a cooling device 11 throughwhich water flows.

Thus it will be seen that the material 1 comprised of a mixture ofthermoplastic material and nonmagnetized permanent magnetic ingredientsis first heated to the plastic temperature of the thermoplastic materialand then advanced longitudinally of the nozzle 5 in such heated state.In effect the nonmagnetized permanent magnetic particles are floating inthis liquid. However, as the mixture comes opposite to the magnets 10,the magnetic particles are free to float and orient themselves inbunches or concentrations corresponding to the positions of the magnets10. The effect is to concentrate the magnetic material at the polepoints.

It is believed that I am the first to ever have mixed nonmagnetizedpermanent magnetic material with a thermoplastic material, heated thethermoplastic material to the liquid or plastic state and then subjectedit to magnetizing forces which are stationary relative to the mixturewhereby the magnetic particles can group or concentrate themselves inaccordance with the magnetizing forces.

FIGURE 2 shows an alternative embodiment of the invention comprised of anozzle 12 through which the material 1 is forced by means of the wormscrew 16, the nozzle 12 being heated by the heating coils 17, 18 as isconventional. The outer end of the nozzle 12 is arcuate and is milledaway so that a portion of the passage of the nozzle 12 is exposed. Awheel 14 having a plurality of magnetizing magnets 13 arranged aroundits periphery rotates in the milled end of the nozzle 12 at a speed suchthat the peripheral velocity of the wheel 14 is the same as the speed ofmovement of the material 1 through the passage.

Cooling means are not shown but may be employed. However, the wheel 14may exert a cooling eifeot on the material 1 as the material comes intocontact therewith.

FIGURE 3 shows the invention as applied to roller calenders. In FIGURE 3the material 19 similar to the material 1 above described is advancedbetween rollers 2%, 22 rotating on parallel axes, then continues aroundthe roller 22 and thence between roller 23 and roller 22. The roller 22as shown has a plurality of permanent magnets 21 extending axially alongits surface and circumferentially spaced. Adjacent magnet-s as shownhave opposite magnetic polarity.

No means are shown for heating the material 19 but it will be understoodthat the material 19 is in a heated state. ternatively, the Wheel 22 canbe heated to an amount sufiicient to heat the material 19.

FIGURE 4 shows a still further alternative emlbodiment of the inventionparticularly applied to an injection mold comprised of two sections 24,25 of nonmagnetic material and defining a mold cavity. A plurality ofmagnetizing magnets 27 are built into the mold cavity in spaced side byside relationship, adjacent magnets having opposite magnetic polarity. Aplate of magnetic material is positioned behind these magnets so as toprovide a magnetic connection of high permeability. Plates 31 ofnonmagnetic material space the magnets 27.

The thermoplastic mixture 29 as above described with reference tomaterial 1 of FIGURE 1 is injected in a heated state into the moldcavity through the nozzle 26 and fills up this mold cavity. The magneticparticles floating in the thermoplastic material migrate in the materialto arrange themselves in concentrated areas corresponding to the linesof magnetic force between the magnets 27. Such concentrations areindicated by the dotted lines 30.

It will thus be appreciated that embodiments of the invention have beendescribed which accomplish all of the objects heretofore set forth andothers and provide a permanent magnetic material which may be readilymolded, has high field strengths for a given weight of permanentmagnetic material together with improved apparatus for producing suchmaterials.

The invention has been described with reference to preferredembodiments. Obviously modifications and alterations will occur toothers upon a reading and understanding of this specification and it ismy intention to include all such modifications and alterations insofaras they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. Apparatus for forming plastically molded permanent magnetic articlesof manufacture comprising in combination an extrusion nozzle at least inpart of nonmagnetic material, means for forcing a thermoplastic materialcontaining powdered nonmagnetized permanent magnetic materials throughsaid nozzle and means for magnetizing the mixture as it goes through theextrusion nozzle comprising a plurality of magnetic poles .and means formoving such poles along said nozzle synchronously with the movement ofthe mixture therethrough.

2. Apparatus for forming continuous lengths of permanent magneticmaterial comprising an elongated forming nozzle at least in part of anonmagnetic material and means for advancing a mixture of athermoplastic material and nonmagnetized particles capable of beingpermanently magnetized through such nozzle and means comprised of atleast a pair of close spaced opposite polarity magnetic poles havingaxes perpendicular to the length of such nozzle and adjacent such nozzlefor subjecting such mixture to a magnetizing force.

3. The combination of claim 2 wherein such means are movablelongitudinally of the nozzle and means are provided for maintaining thespeed of movement synchronous with the speed of movement of the mixturethrough the nozzle.

4. Apparatus for forming continuous lengths of permanent magneticmaterial comprising in combination an extrusion nozzle, means forforcing a mixture of thermoplastic material and nonmaguetized particlescapable of being permanently magnetized through such nozzle, one side ofsaid nozzle being open and means closing said side comprising amagnetizing device including a pair of magnetic poles having an axis ofmagnetization perpendicular to the length of said nozzle.

5. Apparatus for forming continuous sheets of a permanent magneticmaterial comprising in combination a plurality of calender rolls inspaced relationship and rotatable on parallel axes, at least one of saidrolls having a plurality of axially extending circumferentially spacedopposite magnetic poles.

6. A method of forming a permanent magnet body which comprises the stepsof providing a mass of plastic material having finely divided permanentmagnet particles therein, providing a plurality of spaced magnetizingmagnets which present pole faces of opposite magnetic polarity, and,while said mass of material is in .a fiowable condition, moving it alonga predetermined path and forming it into an elongated body of indefinitelength and simultaneously bringing one longitudinal face of saidelongated mass of material and said opposite polarity pole faces of themagnetizing magnets into proximity to each other so that saidmagnetizing magnets magnetize said permanent magnet particles in saidmass and produce continuous spaced apart permanent magnet oles ofalternate polarity at said one longitudinal face of the finished body.

7. A method of forming a permanent magnet body which comprises the stepsof providing a mass of plastic material having finely divided permanentmagnet particles therein, providing a plurality of spaced magnetizingmagnets, and, while said mass of material is in a flowing condition,causing the mass to flow at a predetermined speed along a predeterminedpath of movement and moving said magnetizing magnets along said path ofmovement at the same speed in proximity to said flowing mass tomagnetize said permanent magnet particles in said mass.

8. A method of forming a permanent magnet body which comprises the stepsof providing a mass of plastic material having finely divided permanentmagnet particles therein, heating said mass of material to a flowingcondition and causing the heated mass to flow at a predetermined speedalong a predetermined path of movement, and moving a plurality ofmagnetizing magnets having successive pole faces of alternate polarityalong 6 said path of movement at the same speed with said alter natepolarity pole faces of the magnetizing magnets in proximity to one faceof said flowing mass, to magnetize said permanent magnet particles insaid mass and produce successive spaced permanent magnet poles ofalternate polarity at said one face of the body.

9. The method of claim 8 wherein said mass is extruded through a nozzleand the permanent magnet particles therein are magnetized by saidmagnetizing magnets during such extrusion.

10. The method of claim 8 wherein said mass is extruded through a nozzleand the permanent magnet particles therein are magnetized by saidmagnetizing magnets immediately following such extrusion.

11. The method of claim 8 wherein said mass is passed around calenderingrolls and the permanent magnet particles therein are magnetized by saidmagnetizing magnets during such passage.

12. A method of forming a flexible elongated permanent magnet stripwhich comprises providing a mass of thermoplastic material, mixing inwith said mass finely divided permanent magnet particles, moving aplurality of movable spaced magnetizing magnets having adjacent polefaces of alternate polarity along a predetermined path heating said massof material to a flowing condition and forming it into a strip whichflows at a predetermined speed along a path of travel which is inproximity to a portion of said path of movement of said magnetizingmagnets, and moving said magnetizing magnets at the same speed as saidflowing strip to magnetize said permanent magnet particles in the latterand produce spaced permanent magnet poles of successively alternatepolarity at the adjacent face of the strip.

13. A method of making a permanent magnet body which comprises the stepsof providing a mass of plastic material having finely divided permanentmagnet particles therein, forming said mass into an elongated body,providing spaced magnetizing magnets which present respectively spacedopposite polarity pole faces, and while said mass of material in thebody is in a moving condition bringing one face of the body and saidopposite polarity pole faces of the magnetizing magnets into proximityto each other so that said magnetizing magnets magnetize said permanentmagnet particles in said mass and produce spaced apart permanent magnetpoles of opposite polarity at said one face of the body.

14. A method of making an elongated flexible permanent magnet stripwhich comprises the steps of providing a mass of thermoplastic materialhaving finely divided permanent magnet particles therein, forming saidmass into a continuous elongated strip, providing spaced magnetizingmagnets which present respectively opposite polarity pole faces, andmoving said strip lengthwise past said magnetizing magnets with one faceof the strip in proximity to said opposite polarity pole faces of themagnetizing magnets so that said magnetizing magnets magnetize saidpermanent magnet particles in said mass and produce along the length ofthe strip spaced apart permanent magnet poles of opposite polarity atsaid one face of the strip.

15. Apparatus for magnetizing elongated lengths of a mixture ofnonmaguetized particles capable of being permanently magnetized and aplastic nonmagnetic binder so as to have on one elongated surface, atleast a pair of oppositely polarized permanent magnet poles comprisingin combination: means for moving said mixture along a predeterminedpath, means on said path for continuously forming said mixture into anelongated body of predetermined transverse dimensions, and means formagnetizing said particles as said elongated body moves along said pathincluding at least a pair of close spaced opposite polarity magneticpoles disposed on one side of said path with the axes 0f magnetizationperpendicular to said path.

16. Apparatus for magnetizing elongated lengths of a mixture ofnonmagnetized particles capable of being permanently magnetized and aplastic nonmagnetic binder so as to have on one elongated surface atleast a pair of oppositely polarized permanent magnet poles comprisingin combination: means for moving said mixture along a predeterminedpath, means for changing the transverse dimensions of said mixture andmeans for simultaneously magnetizing said particles as said mixturemoves along said path including at least a pair of close spacedoppositely polarized magnetic poles disposed on one side of said pathwith the axes of magnetization perpendicular to said path.

17. Apparatus for magnetizing elongated lengths of a mixture ofnon-magnetized particles capable of being permanently magnetized and aplastic non-magnetic binder so as to have on one elongated surface aplurality of permanent magnetic poles comprising in combination: meansfor moving Said mixture along a predetermined path, forming means forchanging the transverse dimensions of said mixture, means formagnetizing said particles including a plurality of close spacedmagnetic poles disposed on one side of said path With the axis ofmagnetization perpendicular to said path.

References Cited in the file of this patent UNITED STATES PATENTS HaussAug. 3, Qvastenberg Apr. 30, WeltOn Mar. 18, Parkhurst Feb. 16, FowlerMar. 24, Moxness July 19, Gits July 26, Slaughter Dec. 20, Howell May22, Polydorofi June 17, Berge Oct. 20, Cass July 6, Gross Aug. 17,Rhodes Nov. 2, Bruner et al May 29, Adams et a1. Mar. 4, Rathenau Mar.18, Hakker et a1 June 3,

FOREIGN PATENTS Peterman Aug. 26, Weber Sept. 8,

1. APPARATUS FOR FORMING PLASTICALLY MOLDED PERMANENT MAGNETIC ARTICLESOF MANUFACTURE COMPRISING IN COMBINATION AN EXTRUSION NOZZLE AT LEAST INPART OF NONMAGETIC MATERIAL, MEANS FOR FORCING A THERMOPLASTIC MATERIALCONTAINING, POWDERED NONMAGNETIZED PERMANENT MAGNETIC MATERIALS THROUGHSAID NOZZLE AND MEANS FOR MAGNETIZING THE MATERIAL AS IT GOES THROUGHTHE EXTRUSION NOZZLE COMPRISING A PLURALITY OF MAGNETIC POLES AND MEANSFOR MOVING SUCH POLES ALONG SAID NOZZLE SYNCHRONOUSLY WITH THE MOVEMENTOF THE MIXTURE THERETHROUGH.